Method and Device for Storing Main Information with Associated Additional Information Incorporated Therein

1. A method of creating a watermark by embedding electronic signature data in main data and storing the main data and electronic signature data in a readable form, said method comprising: a supply step of supplying main data, wherein said main data is music performance data complying with MIDI standards and comprises a plurality of MIDI event data; a calculation step of performing a predetermined arithmetic operation using predetermined MIDI event data included in the main data supplied by said supply step; and a change step of changing, in accordance with a predetermined first algorithm and using electronic signature data, a result of the predetermined arithmetic operation performed by said calculation step and changing, in accordance with a predetermined second algorithm and using the changed result of the arithmetic operation, MIDI event data in the main data supplied by said supply step to create a watermark.

2. A method as recited in claim 1 wherein said change step changes, in accordance with said predetermined second algorithm, the MIDI event data in the main data having been used in the predetermined arithmetic operation performed by said calculation step.

3. A method as recited in claim 1 wherein said calculation step performs said predetennined arithmetic operation using a plurality of time-serially different MIDI event data.

4. A method as recited in claim 1 wherein said change step includes a step of extracting part of the electronic signature data to be embedded and said change step changes the performance data using the extracted part of the additional data.

5. A method as recited in claim 1 wherein said calculation step and said change step are repeated until necessary processing is completed for all contents of the electronic signature data to be embedded.

6. A method as recited in claim 5 wherein said calculation step and said change step repeats, a plurality of times, the necessary processing for the all contents of the electronic signature data to be embedded, whereby plural sets of the electronic signature data of same contents are embedded redundantly.

7. A method as recited in claim 1 wherein said change step changes data of predetermined lower bits of the MIDI event data to be changed by the electronic signature data, using the electronic signature data.

8. A method as recited in claim 1 wherein said calculation step and said change step are repeated until necessary processing is completed for all contents of the electronic signature data to be embedded dispersedly in the main data.

9. A method of embedding additional data in main data and storing the main data and additional data in a readable form, said method comprising: a supply step of supplying main data, said main data comprising a plurality of data units, each of the data units representing any one of a plurality of processing instructions; a calculation step of performing a predetermined arithmetic operation using predetermined one or more of the data units included in the main data supplied by said supply step; and a change step of changing, in accordance with a predetermined first algorithm and using additional data, a result of the predetermined arithmetic operation performed by said calculation step and changing, in accordance with a predetermined second algorithm and using the changed result of the arithmetic operation, the main data supplied by said supply step. wherein said main data supplied by said supply step are performance data to be used for reproduction of a music piece and said plurality of data units are a plurality of kinds of event data included in said performance data, and wherein said calculation step calculates a difference between two time-serially different event data of the event data representing a particular processing instruction in the performance data, and wherein said change step changes, in accordance with said predetermined first algorithm and using the additional data, said difference calculated by said calculation step and changes, in accordance with said predetermined second algorithm and using the changed difference, the performance data supplied by said supply step.

10. A method as recited in claim 9 which further comprises a step of classifying, on the basis of a level of the difference calculated by said calculation step, said event data representing a particular processing instruction into any one of a plurality of groups, and wherein said change step changes, for each of the groups, said event data representing a particular processing instruction in accordance with a predetermined algorithm and using the additional data and the difference calculated by said calculation step.

11. A method of uncovering a watermark by reproducing electronic signature data embedded in main data, said method compnsing: a reception step of receiving main data, wherein said main data is music performance data complying with MIDI standards and comprises a plurality of MIDI event data, at least one of the MIDI event data changed by electronic signature data; a calculation step of performing an arithmetic operation in accordance with a predetermined algorithm and using predetermined MIDI event data included in the main data received by said reception step; and a reproduction step of reproducing the electronic signature data on the basis of a result of the arithmetic operation performed by said calculation step to uncover a watermark.

12. A method as recited in claim 11 wherein said main data received by said reception step is data which is read out from a memory.

13. A method as recited in claim 11 wherein said main data received by said reception step are data which has been received via a communication line.

14. A method as recited in claim 11 wherein plural sets of the electronic signature data of same contents are embedded redundantly in the main data to be received by said reception step.

15. A method as recited in claim 11 wherein said calculation step performs the arithmetic operation in accordance with the predetermined algorithm and using time-serially different MIDI event data included in the main data received by said reception step.

16. A method as recited in claim 11 wherein all contents of the electronic signature data are embedded dispersedly in the main data to be received by said reception step.

17. A method as recited in claim 11 which further comprises a display step of visually showing at least part of the electronic signature data reproduced by said reproduction step.

18. A method as recited in claim 11 wherein the electronic signature data are embedded in data of predetermined lower bits of the MIDI event data to be received by said reception step.

19. A method of reproducing additional data embedded in main data, said method comprising: a reception step of receiving main data comprising a plurality of data units, each of said data units representing any one of a plurality of processing instructions, at least one of the data units in the main data being changed by additional data; a calculation step of performing an arithmetic operation in accordance with a predetermined algorithm and using predetermined data units included in the main data received by said reception step; and a reproduction step of reproducing the additional data on the basis of a result of the arithmetic operation performed by said calculation step, wherein said calculation step calculates a difference between the at least two time-serially different data used in the arithmetic operation according to the predetermined algorithm and any one of a plurality of algorithms that is selected in accordance with the difference is used as said predetermined algorithm.

20. An apparatus for creating a watermark by embedding electronic signature data in main data and storing the main data and electronic signature data in a readable form, said apparatus comprising: a supply section that supplies main data, wherein said main data is music performance data complying with MIDI standards and comprises a plurality of MIDI event data; a calculation section that performs a predetermined arithmetic operation using predetermined MIDI event data included in the main data supplied by said supply section; and a change section that changes, in accordance with a predetermined first algorithm and using electronic signature data, a result of the predetermined arithmetic operation performed by said calculation section and changes, in accordance with a predetermined second algorithm and using the changed result of the arithmetic operation, MIDI event data in the main data supplied by said supply section to create a watermark.

21. An apparatus for uncovering a watermark by reproducing electronic Signature data embedded in main data, said apparatus comprising: a reception section that receives main data, wherein said main data is music performance data complying with MIDI standards and comprises a plurality of MIDI event data, at least one of the MIDI event data changed by electronic signature data; a calculation section that performs an arithmetic operation in accordance with a predetermined algorithm and using predetermined MIDI event data included in the main data received by said reception section; and a reproduction section that reproduces the electronic signature data on the basis of a result of the arithmetic operation preformed by said calculation section to uncover a watermark.

22. An apparatus for embedding additional data in main data and storing the main data and additional data in a readable form, said apparatus comprising: a supply section that supplies main data, said main data is performance data to be used for reproduction of a music piece and comprises a plurality of data units, said plurality of data units are a plurality of kinds of event data included in said performance data and each of the data units represents any one of a plurality of processing instructions; a calculation section that performs a predetermined arithmetic operation using predetermined one or more of the data units included in the main data supplied by said supply section, said predetermined arithmetic operation calculates a difference between two time-serially different event data of the event data representing a particular processing instruction in the performance data; and a change section that changes, in accordance with said predetermined first algorithm and using the additional data, said difference calculated by said calculation section and changes, in accordance with said predetermined second algorithm and using the changed difference, the performance data supplied by said supply section.

23. An apparatus for reproducing additional data embedded in main data, said method comprising: a reception section that receives main data, said main data is performance data to be used for reproduction of a music piece and comprises a plurality of data units, said plurality of data units are a plurality of kinds of event data and each of said data units represents any one of a plurality of processing instructions, at least one of the data units in the main data is changed by additional data; a calculation section that performs an arithmetic operation in accordance with the predetermined algorithm and using at least two time-serially different data of particular event data included in the performance data, said arithmetic operation calculates a difference between the at least two time-serially different data used in the arithmetic operation according to the predetermined algorithm and any one of a plurality of algorithms that is selected in accordance with the difference is used as said predetermined algorithm; and a reproduction section that reproduces the additional data on the basis of a result of the arithmetic operation performed by said calculation section.